1. Field of the Invention
The instant invention relates to the construction of frameless cargo-carrying containers and trailer bodies, of the sort which are adapted to be suitably hauled by tractor units.
The term, "container," as used herein, designates a closed, hollow structure of substantially rectangular or square cross-section having a length of at least about ten feet, a width of at least about eight feet and a height of at least about four feet. In one embodiment of the invention, a "container" may be mounted on a frame, supported by one or more bogies, and transported by being suitably connected to a tractor unit. A bulk cargo "container" may be filled with a pourable bulk cargo, such as grain or plastic beads, shipped on a suitable vessel, and discharged at its port of destination. "Containers" may be transported, in stacked relationship, in the hold or on a deck of a ship, on railroad cars, such as flat-bed cars, or like well-known means.
The term, "trailer body," as used herein, designates a closed hollow storage unit of substantially rectangular or square cross-section, having a length of at least about twenty feet, a width of at least about eight feet, and a height of at least about eight feet, and which includes integral fittings at the base thereof to which running gear, landing gear, and king pin are fastened. A "trailer body" is adapted to be hauled over-the-road, by a tractor unit and is not usually used to transport cargo by ship or by rail, except as an entire unit with bogies attached.
As used herein, the term, "frameless," designates a container or trailer body in which a substantial portion, at least about 67 percent, and preferably at least about 75 percent, of the load caused by the presence of cargo in the container or trailer body and created by dynamic forces during operation of vehicle is borne by the sides of the container or trailer body. Thus, the walls of a "frameless" container or trailer body are capable of safely withstanding stresses in the range from about 15,000 p.s.i. to about 25,000 p.s.i., which stresses are caused by the weight of the cargo in the container or trailer body, and by the dynamic forces initiated by the operation of the vehicle.
2. The State of the Art
Aluminum has been used, for many purposes, as a material of choice in the manufacture of cargo-carrying containers and trailer bodies, for some period of time. The manner in which aluminum has been used, in the formation of the side and end panels of trailer bodies or containers, was to incorporate a plurality of individual aluminum sheets having dimensions which typically were two feet by nine feet, into each of the sides and the end, and to mount the individual aluminum sheets of each side or end, at their interfaces, to aluminum or steel structural stiffener members, which are typically hat-shaped channels.
Unitary plywood panels, coated on either face with fiberglass-reinforced polyester, have been used as side panels and as end panels in cargo-carrying containers and trailer bodies, in conjunction with aluminum structural members. These aluminum structural members include channels to which the edges of the fiberglass-reinforced plywood panels are secured by bolts.
It is desirable to be able to fabricate an all aluminum alloy or mostly aluminum alloy cargo-carrying container or trailer body, in order to overcome some of the shortcomings of the foregoing prior art constructions.
The frameless aluminum or steel stiffener-reinforced aluminum side panel container and trailer body constructions of the prior art are easily damaged and their joints, where the aluminum sheets are fastened to the stiffeners, may be loosened whereby expensive maintenance is required. The aluminum or steel stiffeners of these units decreases the interior, cargo-carrying volume of the container, for any specific size of container having given exterior volume, because of the internal space occupied by the stiffeners. Such reinforced units are quite heavy when the stiffeners are made of steel, a factor contributing to additional tire wear and tractor engine wear, and reducing profitable payload by limiting the amount of payload that can be transported by truck, sea or rail since the gross weight (gross weight including the weight of cargo and the weight of the cargo-carrying unit) of any loaded container or trailer body is limited.
The shortcomings of the prior art frameless fiberglass reinforced-plywood side panel and end panel container and trailer body units have been the substantial weight of these units; the difficulty of fabricating such units, because of the inability to weld fiberglass reinforced-plywood panels to the support channels; the loss of inner volume due to panel thickness and the need for channels and bolts or rivets to join the panels to the support members; the deterioration of the plywood panels due to coating imperfections; and natural organic deterioration of the wood.
The instant invention overcomes the foregoing shortcomings of the prior art by providing an aluminum alloy frameless cargo-carrying container or trailer body construction, formed of unitary aluminum alloy plate side panels and end panel having a thickness of at least 5/32" and tensile yield strength of at least 25,000 p.s.i., thereby providing a noncorrosive and therefore long-lived, substantially maintenance free, frameless container or trailer body construction which has increased interior cargo-carrying volume for a given exterior volume; is relatively light in weight per square foot of available floor space; resists damage due to abuse; has a high scrap value; does not need painting; and is relatively economical to fabricate.